The right of priority under 35 U.S.C. xc2xa7119(a) is claimed based on German Patent Application No. 101 21 001.9, filed Apr. 28, 2001, the entire disclosure of which is hereby incorporated by reference.
The present invention relates to a one-piece multi-passageway flat tube with folded webs, and to a method of manufacturing such a multi-passageway flat tube. The invention also relates a heat exchanger embodying at least one such multi-passageway flat tube.
Flat tubes of this general type are disclosed in commonly-assigned European Patent EP 0 302 232 B1. Such a tube is made from a metal strip, and the webs for forming the individual passageways are produced by folding the metal strip. These webs are consequently double-walled and, at their bending site, form a web ridge which is brazed to the inside of the flat tube. The longitudinal seam of such a flat tube can likewise be produced by brazing. The metal strip is preferably clad with brazing material on both sides, so that brazing is possible on both the inside and the outside of the flat tubes.
Another construction for a folded multi-passageway tube is disclosed in U.S. Pat. No. 5,386,629 or European Patent EP 0 457 470, wherein the design of the longitudinal seam differs in that, in this case, it is arranged on the narrow side of the flat tube and produced by butt-welding or brazing.
Further embodiments of folded multi-passageway flat tubes, which are made from a flat sheet-metal strip and brazed together, are disclosed in commonly-owned German Utility Model 299 06 337 and also in EP-A 1 074 807.
The flat tubes mentioned above are used as both coolant tubes for coolant heat exchangers and refrigerant tubes for condensers in vehicle air-conditioning systems. In particular in the case of refrigerant condensers, high heat transfer capacity is desired, for which reason the hydraulic diameter of the individual passageways is dimensioned very small, that is to say in the range of one to two millimeters. These tubes nevertheless still have potential for increasing the heat transfer capacity.
One principal object of the present invention is to provide a one-piece folded multi-passageway tube improved with regard to its heat transfer capability. A further object of the invention is to provide improved methods for producing the improved multi-passageway tubes. A still further object of the invention is to provide improved heat exchangers embodying the tubes according to the invention, as well as improved automotive heating/air-conditioning systems embodying such heat exchangers.
In accordance with one aspect of the present invention, there has been provided a multi-passageway flat tube, comprising: a sheet metal strip folded into the form of a generally flat tube and having a longitudinal seam, wherein the folded metal sheet includes at least one folded web directed toward the inside of the flat tube and having two walls forming a common contact surface and a web ridge, the web ridge being brazed to at least one inner wall of the fiat tube to form multiple axially extending passageways within the tube, and wherein the web includes at least one through-opening to permit communication between the passageways and is brazed in at least part of the area of the contact surface.
In accordance with another aspect of the invention, there is provided a method of manufacturing a multi-passageway flat tube as defined above, which comprises: providing an endless, flat sheet metal strip; punching the through-openings according to a predetermined pattern; folding the sheet metal strip to form webs, so that one adjacent through-opening meets a corresponding adjacent through-opening; forming the sheet metal strip containing the webs into a closed multi-passageway flat tube cross section; and brazing the web ridges to the opposing inner wall of the flat tube or to respective opposing web ridges and brazing the longitudinal seam.
According to yet a further aspect of the invention, there has been provided another method of manufacturing a multi-passageway flat tube, which comprises: providing an endless, flat sheet metal strip; folding the sheet metal strip to form the webs; fashioning notches in the web ridges by stamping or rolling; forming the sheet metal strip containing the webs into a closed multi-passageway flat tube cross section; and brazing the web ridges to the inner wall of the tube or to corresponding opposing web ridges and brazing the longitudinal seam.
Still another method is provided of manufacturing a multi-passageway flat tube, which comprises: providing an endless, flat sheet metal strip; producing the at least one slit according to a predetermined pattern; folding the sheet metal strip to form the webs, so that one adjacent slit meets another adjacent slit; de-forming at least one slit edge; forming the sheet metal strip containing the at least one edge into a closed multi-passageway flat tube cross section; and brazing the web ridges to the opposing inner wall of the tube or to corresponding opposing web ridges and brazing the longitudinal seam.
According to a further aspect of the invention, there has also been provided a method of manufacturing a multi-passageway flat tube, which comprises: providing an endless, flat sheet metal strip; folding the sheet metal strip to form the webs; forming the web ridges into an undulating shape; forming the sheet metal strip containing the undulating shape into a closed multi-passageway flat tube cross section; and brazing the web ridges to the opposing inner wall of the tube or to respective opposing web ridges and brazing the longitudinal seam.
Another aspect of the invention involves a heat exchanger suitable for use in a motor vehicle, comprising at least one header and at least one multi-passageway flat tube opening into the header, wherein the at least one multi-passageway flat tube comprises a multi-passageway flat tube as defined above.
Finally, the invention provides as another aspect a motor vehicle air-conditioning system, comprising at least one refrigerant-carrying heat exchanger, wherein the heat exchanger comprises a heat exchanger as defined above.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying figures of drawing.